1. Field of the Invention
The present invention relates to an improved clamping mechanism for clamping the strings of a stringed instrument, such as a guitar. More specifically, the invention relates to a simplified clamping mechanism, wherein the individual strings of the instrument are held between laterally movable blocks, and wherein at least one of the blocks is engaged by an urging means which urges it in the direction of a stationary block, which is arranged on the other side of a string therefrom. The urging means is formed such that it is disposed entirely to one side of the block upon which it acts, so that the need to pass a bolt under the strings of the instrument is avoided, and thickness of the of the portion of the clamping mechanism which extends under the strings of the instrument can be reduced.
2. Description of the Prior Art
Clamping nuts, for preventing the strings of musical instruments, particularly guitars, from slipping across the nut and going out of tune, have become increasingly popular. An excellent example of such a nut is set forth in U.S. Pat. No. 4,475,432 issued Oct. 9, 1984. In this device a plurality of blocks are arranged in a groove in the nut of a guitar, so as to be longitudinally slidable therewithin. The blocks have registered holes aligned along the long axis of the slot in the nut. A bolt is inserted through the registered holes in the blocks, and is threaded into one of the end blocks. The strings of the instrument are arranged in the gaps between the blocks. When the bolt is tightened, the blocks are driven together, and the strings become clamped in the gaps between the blocks.
The above device is extremely convenient because all of the strings of the instrument can be clamped at once by tightening the bolt, and because the strings are arranged to pass over the top of the bolt and therefore don't need to be threaded through a small hole, as in other types of clamping nut devices. Instead, they are slid, from above, into the gaps between the blocks while the bolt is in a loosened state.
The above device however has the following disadvantages. The end block which engages the threads of the bolt, and the other end block, which is engaged by the head of the bolt, tend to twist in the groove due to friction when the bolt is turned. This twisting of the blocks tends to cause the strings of the instrument to go out of tune when the nut is tightened.
The above disadvantages can be avoided by forming the blocks and groove very precisely so as to eliminate any room for play. Achieving this precision tends to make the units expensive to produce.
Solutions to the problems of the spacer rotation and formation of the groove for the spacers were proposed by the authors in U.S. patent application Ser. No. 242,425 wherein it was proposed that the spacer blocks be formed as cylinders having a flat side, or a keyway, to prevent them from rotating, and that the groove be formed as a cylinder with the top portion open.
In the later device however, another disadvantage occuring in all the above devices, remains unresolved. This problem being that the bolt, by which the blocks are driven together, passes through the centers of the blocks, and under the strings at the nut of instrument, with respect to the heal or the headstock. Thus, the effective clamping portion of the blocks, is limited to that space above the top of the bolt, and there is a rather large dead space, in the gaps between the spacers, beneath the effective clamping portions.
The net effect of this is that the portion of the nut lying beneath the level of the lowest string, must be equal to the thickness of the bolt, plus the thickness of the portion of the spacer block lying between the bolt and the lower web of the channel portion of the nut, plus the thickness of the web itself, which must be substantial so as to provide the degree of stiffness required to prevent the sides of the channel portion from spreading. This means that a rather deep groove must be made in the neck of the instrument, to accommodate the nut. Forming this groove requires skilled labor, and it weakens the juncture between the peg head of the instrument an the neck, which can cause it to break more easily if the instrument is accidentally mishandled.
A further problem in the above devices lies in the fact that the center block must be fastened to the channel member in order to prevent the blocks from sliding laterally within the groove. This means that some fastening means such as a threaded hole must be formed in the block. This has the result of adding a production step to the manufacture of the center blocks. This increases the production cost.